Alkaline dry batteries have an inside-out structure. A hollow cylindrical positive electrode mixture is disposed in a positive electrode case serving also as a positive electrode terminal, so as to closely contact with the positive electrode case. A gelled negative electrode is disposed in the center of the positive electrode mixture with a separator interposed therebetween. With widespread proliferation of digital devices in recent years, the load power of the devices using batteries as a power supply thereof has been gradually increasing. And therefore, there have been demanded batteries having excellent discharge characteristics under heavy load. In order to respond to such demands, Patent Document 1 proposes mixing a nickel oxyhydroxide powder to a positive electrode mixture. Batteries including nickel oxyhydroxide in the positive electrode have excellent discharge characteristics under heavy load, and have resulted in practical use in recent years.
Alkaline dry batteries including a nickel oxyhydroxide powder as a positive electrode active material have more excellent discharge characteristics under heavy load compared with those of conventional alkaline dry batteries. Therefore, the alkaline dry batteries are spreading as a main power supply for digital devices represented by digital cameras. However, digital devices, for example, digital cameras, have various functions such as light emission of stroboscopes, extending and retracting of optical lens, displaying of liquid crystals, and writing of image data to recording media. Accordingly, batteries used as a power supply of the digital devices need to be able to instantaneously supply electric power under heavy load depending on various functions.
In alkaline dry batteries including a nickel oxyhydroxide powder in a positive electrode active material, storage in an environment at high temperature increases the resistance between the positive electrode case and the positive electrode mixture, and also decreases the amount of the dischargeable positive electrode active material. Therefore, the alkaline dry batteries have a problem that their heavy-load discharge characteristics after storage in an environment at high temperature inferior to those of alkaline manganese batteries not including the nickel oxyhydroxide powder. In order to cope with this problem, Patent Document 2 has proposed addition of zinc oxide and calcium oxide to the positive electrode mixture.    Patent Document 1: Japanese Laid-Open Patent publication No. 2000-48827    Patent Document 2: Japanese Laid-Open Patent publication No. 2001-15106